How to init my array in swift

I have this code for a question and answer app i want to make. It is supposed to ask a random question from the array.
My code is working in playground, but when i put it into an xcode project, it tells me:

Cannot use instance member 'Kat1' within property initializer; property initializers run before 'self' is available

Im new to coding apps and swift, and i dont know how to init the array the right way.